Organisation: Johannes Gutenberg University Mainz > Faculty 08 > Institute of Nuclear Physics > Theory Group
Research: Johannes Gutenberg University Mainz > Faculty 08 > Physics > Nuclear and Hadronic Theory

The theory group's research activities focus on investigations of the strong interaction at energies relevant to the theoretical interpretation of the experiments at MAMI and at other accelerator facilities. We use both analytical methods like effective field theories and dispersion theory, and numerical simulations of nuclear structure and lattice QCD.

The basic observables for the understanding of the structure of the nucleon and its excited states are form factors, structure functions and parton distributions. The theoretical study of these observables are the basis for the interpretation of the experiments at MAMI, JLab, COMPASS as well as for future projects like PANDA.

The anomalous magnetic moment (g-2) of the muon has been measured with extremely high precision. A similarly accurate theoretical prediction, which is needed to probe the limits of the Standard Model in the leptonic sector, requires a thorough understanding of the hadronic contributions to (g-2) from non-perturbative QCD.

The calculation of weak hadronic matrix elements with lattice QCD is a central component for the determination of the elements of the CKM-matrix, and the study of CP violation in the Standard Model, as well as for searches for physics beyond the Standard Model from precise measurements of hadron lifetimes and branching fractions.

Experimental studies made to assess where our theoretical understanding of nature has its limits, and where possibly so far unobserved new worlds of matter are waiting to be discovered and understood, are complemented by calculations in lattice QCD.

In order to help interpret experiments in low-energy nuclear physics that will be performed in the future MESA facility, as well as in other laboratories world-wide, forefront nuclear theories need to be developed. We are active both in nuclear structure theory and in reactions theory.

K. Ottnad, G. von Hippel

2025

A. Barone, D. Djukanovic, G. von Hippel, J. Koponen, H.B. Meyer, K. Ottnad, H. Wittig

2025

P. Kalamidas, M. Vanderhaeghen

2025

B. Acharya, J.E. Sobczyk, S. Bacca, G. Hagen, W. Jiang

2024

K. Ottnad, G. von Hippel

2025

M. Gorchtein, V. Katyal, B. Ohayon, B.K. Sahoo, C.-Y. Seng

2025

J. Parrino, V. Biloshytskyi, E.-H. Chao, H.B. Meyer, V. Pascalutsa

2025

D. Ruth, K. Slifer, J.-P. Chen, C.E. Carlson, F. Hagelstein, V. Pascalutsa, A. Deur, S. Kuhn, M. Ripani, X. Zheng, R. Zielinski, C. Gu

2024

We use a variety of theoretical tools and techniques to study hadronic and nuclear physics from first principles.

Lattice QCD is a model-independent and mathematically rigorous first-principles approach to studying nonperturbative Quantum Chromodynamics (QCD) using a discrete spacetime lattice which can be simulated on a computer. Putting the quark fields on the sites of the lattice and the gauge fields on the links connecting neighbouring sites, the path integral for QCD can be written as a probability distribution over a very large space of configurations, which can be efficiently sampled using Monte-Carlo simulations. To fully control all systematic uncertainties, extrapolations to vanishing lattice spacing and infinite lattice volume are required.

Chiral Perturbation Theory is an effective field theory for the low-energy regime of QCD, which is based on the approximate chiral symmetry of QCD with light quarks and uses light pseudoscalar mesons (pions, kaons, ...) as the relevant degrees of freedom. Further extensions can be made to incorporate baryons, vector mesons and heavy-quark mesons. Chiral Perturbation Theory is important, among other things, to make the connection between lattice simulations at unphysical quark masses and the real world.

The locality and causality of Green functions in Quantum Field Theory enables a description of their analytic structure in terms of integrals along cuts in the complex plane. This general idea gives rise to tools such as the Källén-Lehmann spectral representation, the optical theorem and sum rules, which can be used to derive rigorous bounds on various quantities in terms of experimentally observable cross sections.

Few-body methods are essential tools for the study of light nuclei, where the number of nucleons is small enough to allow for exact or near-exact solutions of the Schrödinger equation using realistic two- and three-nucleon interactions. Approaches such as the hyperspherical harmonics method enable accurate predictions of bound states, scattering observables, and response functions. By leveraging these techniques, we gain deep insight into the structure and dynamics of light nuclei, while also testing and constraining nuclear forces.

Many-body methods such as coupled-cluster (CC) theory are powerful and systematically improvable ab initio approaches for describing the structure of medium-mass nuclei, typically ranging from oxygen to tin. CC theory has been successfully adapted to nuclear physics due to its ability to capture a significant portion of many-body correlations while maintaining computational tractability. It is particularly effective for closed-shell nuclei and their neighbours, and has been extended to include three-nucleon forces and continuum effects, enabling precise predictions of binding energies, excitation spectra, radii, and, more recently, electroweak reactions.

Effective field theories (EFTs) offer a systematic approach to describing nuclear interactions at low energies by exploiting a separation of scales. In nuclear physics, chiral EFT is widely used to derive two- and many-body forces, as well as electroweak currents, in a way that is consistent with the symmetries of QCD, particularly chiral symmetry. Complementing this, halo EFT is a specialized framework tailored to describe weakly bound systems—such as halo nuclei—where a clear separation exists between the core and valence nucleons. It is particularly powerful in reaction theory, making it a valuable tool for interpreting experiments near the drip lines.

A deep dive into nucleon structure - exploring open problems at the intersection of nuclear, particle and atomic physics
Instructor: Dr. Dalibor Djukanovic; Univ.-Prof. Dr. Tyler Kutz; Dr. Vladimir Pascalutsa; Univ.-Prof. Dr. Randolf Pohl
Arbeitsgruppenseminar zu aktuellen Themen in der Theoretischen Kern- und Elementarteilchenphysik
Instructor: Prof. Dr. Jens Erler; Mikhail Gorshteyn; apl. Prof. Dr. Hubert Spiesberger
Arbeitsgruppenseminar zu speziellen Problemen der Gittereichtheorie
Instructor: Univ-Prof. Dr. Harvey Meyer; Univ.-Prof. Dr. Hartmut Wittig; apl. Prof. Dr. Georg von Hippel
Arbeitsgruppenseminar zur Ab-initio theoretischen Kernphysik
Instructor: Univ.-Prof. Dr. Sonia Bacca
Arbeitsgruppenseminar zur Theoretischen Kernphysik
Instructor: Univ.-Prof. Dr. Marc Vanderhaeghen
Einführung in die Gittereichtheorie
Instructor: apl. Prof. Dr. Georg von Hippel
Gebietsübergreifende Konzepte
Instructor: apl. Prof. Dr. Frank Fiedler; Prof. Dr. Stefan Scherer
Mathematische Rechenmethoden
Instructor: Univ.-Prof. Dr. Sonia Bacca
Mathematische Rechenmethoden 1
Instructor: apl. Prof. Dr. Georg von Hippel
Mathematische Rechenmethoden 2
Instructor: Prof. Dr. Stefan Scherer
Theoretische Elektrodynamik
Instructor: Dr. Dalibor Djukanovic
Theoretische Physik 1, Theoretische Mechanik
Instructor: Univ.-Prof. Dr. Hartmut Wittig
Theoretische Physik 3, Quantenmechanik
Instructor: Univ.-Prof. Dr. Marc Vanderhaeghen
Theoretische Physik 6a, Relativistische Quantenfeldtheorie
Instructor: Prof. Dr. Jens Erler
Theoretische Quantenphysik
Instructor: Prof. Dr. Stefan Scherer
Writing Matters
Instructor: apl. Prof. Dr. Pierre Capel

SoSe 2026

Symmetrien in der Physik